Oral glucose tolerance test for acromegaly

Using glucose to check a growth-hormone brake
Clinical review September 2026

This is not an ordinary diabetes test
In healthy physiology, drinking glucose tells growth hormone to fall. In suspected or monitored acromegaly, the oral glucose tolerance test (OGTT) measures whether that brake works. It is used alongside IGF-1 and clinical information; it is not a standalone test for every person with a headache, large shoes or a high random growth-hormone result.

What happens on the day
You will usually be asked to fast and to follow specific instructions about exercise, alcohol, smoking and medicines. A baseline sample is taken, a measured glucose drink is consumed, and further blood samples are collected over the next couple of hours. The drink can be sweet and some people feel briefly nauseated. Bring something suitable to eat afterwards unless advised otherwise.

What the curve can and cannot say
In acromegaly, growth hormone may fail to suppress adequately after glucose. Assay methods and cut-offs vary, so results are interpreted by the same specialist laboratory where possible and alongside IGF-1. Pregnancy, diabetes, liver disease, kidney disease, puberty and oestrogen treatment can alter interpretation. If you have diabetes or take glucose-lowering medicines, the team needs to plan the test safely rather than simply issuing the standard fasting leaflet.

Important safety note
This page is general education, not personal medical advice. Seek urgent help for sudden severe headache, new visual loss or double vision, collapse, confusion, seizure, or acute severe illness. Follow individual instructions from your endocrine team for medicines and investigations.

Further reading

• Acromegaly diagnostic consensus